Transformers

Hugging Face Transformers gives you access to 400,000+ pre-trained models with a consistent Python API for text generation, translation, summarization, image classification, and more. Load a model in three lines of code, run inference, done.

Apache 2.0. This is the standard library for working with transformer models. PyTorch, TensorFlow, and JAX backends. The `pipeline` API lets you go from zero to a working model in literally one line: `pipeline('sentiment-analysis')('I love this')`. For fine-tuning, the Trainer API handles the training loop, checkpointing, and evaluation.

The library is free. Hugging Face Hub (the model hosting platform) has a free tier with unlimited public models and 25GB private storage. Pro ($9/mo) adds more private storage. Enterprise plans exist for organizations needing governance and deployment at scale.

The catch: running large models requires serious GPU hardware. A 7B parameter model needs ~14GB VRAM just for inference. The library is free but the compute is not. Hugging Face Inference Endpoints (managed deployment) starts at $0.06/hr for CPU, $0.60/hr for GPU. Also, the library is enormous; it pulls in PyTorch (~2GB) and the ecosystem of dependencies is heavy. For production inference specifically, look at vLLM or llama.cpp for better performance.